Wells are generally drilled into the ground or ocean bed to recover natural deposits of oil and gas, as well as other desirable materials that are trapped in geological formations in the Earth's crust. Wells are typically drilled using a drill bit attached to the lower end of a “drill string.” Drilling fluid, or mud, is typically pumped down through the drill string to the drill bit. The drilling fluid lubricates and cools the bit, and may additionally carry drill cuttings from the borehole back to the surface.
In various oil and gas exploration operations, it may be beneficial to have information about the fluids contained in the subterranean formations that are penetrated by a borehole. For example, certain formation evaluation schemes include measurement and analysis of the fluids extracted from the subterranean formations. These measurements may be essential to designing the production facility and predicting the lifetime thereof.
Reservoir well creation and/or testing may involve drilling into the subterranean formation and the monitoring of various subterranean formation parameters. As such, downhole tools may be exposed to increasingly hostile environments, such as by having increased downhole pressure, temperature, increased level of shock and vibration, in addition to increasingly corrosive environments. For example, as the corrosivity of downhole environments increases, the useful life of the downhole tools in these environments may be reduced, such as by limiting the useful life of the downhole tools to only 100 to 200 hours while downhole. In addition, as the corrosivity of subterranean formation fluids increases, these formation fluids may influence the choice of materials to be used in production facilities and/or reduce the useful life of such production facilities.
Corrosivity is normally increased in high sulfide and/or carbon dioxide environments, as well as in aqueous environments having a large concentration of sodium chloride, such as those environments present in the Middle East.